Fluid or hydraulic mountings include a fluid to augment isolation and/or damping characteristics achievable within elastomer mountings alone. This augmentation may take the form of additional parasitic damping or added inertial forces. Fluid mountings are generally described in LORD.RTM. Technical Article LL-2166 entitled "Understanding Hydraulic Mounts for Improved Vehicle Noise, Vibration and Ride Qualities" by W. C. Flower. Commonly assigned U.S. Pat. No. 4,811,919 to Jones describes a double-acting fluid mounting which incorporates a volume compensator. Other examples of fluid devices may be found in commonly assigned U.S. Pat. Nos. 5,540,549 to McGuire, 5,501,434 to McGuire, 5,413,320 to Herbst, 5,374,039 to Schmidt et al., 5,197,692 to Jones et al., and 5,127,607 to McGuire. Fluid mountings and dampers are, in essence, tunable passive devices which use a fluid to add additional tuned "damping" or tuned-fluid "inertia" effects.
Relating to fluid and elastomer dampers, such as those used to dissipate large amounts of energy and to control motions, such as the lead-lag motions of helicopter rotor blades, high damping forces are desired. Further, because the lead-lag damper is exposed to the wind stream caused by rotation of the rotor system, the damper must exhibit a small profile, such that aerodynamic drag is minimized. In particular, a concomitant result of dissipating such large amounts of energy is heat buildup within the damper, which may prematurely degrade the damper's performance. Therefore, designs which are thermodynamically efficient are desired. In addition, compensation of fluid thermal expansion and contraction, pressurization, and fill to remove air bubbles are all problems.
Therefore, there is a recognized need for more, smaller, thermodynamically efficient dampers as well as for dampers which include efficient expansion, pressurization, and fill characteristics.